The PCI (Peripheral Component Interconnect) bus emerged in the early 1990s when a broad range of IO (input/output) buses existed in the PC (personal computer) field, such as a VESA (Video Electronics Standards Association) local bus, an EISA (Extended Industry Standard Architecture) bus, and an ISA (Industry Standard Architecture) bus. At the earliest stage, the PCI emerged in place of the ISA bus. In that period, a 33 MHz (megahertz) PCI bus fully satisfied the data transmission application. With the rapid increase of the processing capability of a processor and the read and write speeds of the memory, the PCI bus quickly evolved from a 33 MHz PCIE bus to a 66 MHz PCIE (PCI-Express) bus. The PCIE device is widely adopted in the IT (information technology) field, especially the PCIE graphics card is applied massively. The energy-saving research of the PCIE device is one of the current hot topics.
Currently, the PICE energy-saving technology includes two energy-saving modes: power management (PM) and link active-state power management (ASPM). A power management state “D” of a PCIE device and a power management state “L” of a PCIE link are defined. In an actual use process, the two energy-saving modes, that is, a PCIE device enters the power management state D and a PCIE link enters the power management state L, are implemented independently, and the overall energy-saving efficiency is not high.